The Alberta Newborn Screening Approach for Sickle Cell Disease: The Advantages of Molecular Testing.

Sickle cell disease (SCD), a group of inherited red blood cell (RBC) disorders caused by pathogenic variants in the beta-globin gene (HBB), can cause lifelong disabilities and/or early mortality. If diagnosed early, preventative measures significantly reduce adverse outcomes related to SCD. In Alberta, Canada, SCD was added to the newborn screening (NBS) panel in April 2019. The primary conditions screened for are sickle cell anemia (HbS/S), HbS/C disease, and HbS/ß thalassemia. In this study, we retrospectively analyzed the first 19 months of SCD screening performance, as well as described our approach for screening of infants that have received a red blood cell transfusion prior to collection of NBS specimen. Hemoglobins eluted from dried blood spots were analyzed using the Bio-Rad™ VARIANT nbs analyzer (Bio-Rad Laboratories, Inc., Hercules, CA, USA). Targeted sequencing of HBB was performed concurrently in samples from all transfused infants. During the period of this study, 43 of 80,314 screened infants received a positive NBS result for SCD, and of these, 34 were confirmed by diagnostic testing, suggesting a local SCD incidence of 1:2400 births. There were 608 infants with sickle cell trait, resulting in a carrier frequency of 1:130. Over 98% of non-transfused infants received their NBS results within 10 days of age. Most of the 188 transfused infants and 2 infants who received intrauterine transfusions received their final SCD screen results within 21 ± 10 d of birth. Our SCD screening algorithm enables detection of affected newborns on the initial NBS specimen, independent of the reported blood transfusion status.

Is impaired energy production a novel insight into the pathogenesis of pyridoxine-dependent epilepsy due to biallelic variants in ALDH7A1?

BACKGROUND: Pyridoxine-dependent epilepsy (PDE) is due to biallelic variants in ALDH7A1 (PDE-ALDH7A1). ALDH7A1 encodes α-aminoadipic semialdehyde dehydrogenase in lysine catabolism. We investigated the gamma aminobutyric acid (GABA) metabolism and energy production pathways in human PDE-ALDH7A1 and its knock-out aldh7a1 zebrafish model. METHODS: We measured GABA pathway, and tricarboxylic acid cycle metabolites and electron transport chain activities in patients with PDE-ALDH7A1 and in knock-out aldh7a1 zebrafish. RESULTS: We report results of three patients with PDE-ALDH7A1: low paired complex I+II and complex II+III and individual complex IV activities in muscle biopsy in patient 1 (likely more severe phenotype); significantly elevated CSF glutamate in the GABA pathway and elevated CSF citrate, succinate, isocitrate and α-ketoglutarate in the TCA cycle in patient 3 (likely more severe phenotype); and normal CSF GABA pathway and TCA cycle metabolites on long-term pyridoxine therapy in patient 2 (likely milder phenotype). All GABA pathway metabolites (γ-hydroxybutyrate, glutamine, glutamate, total GABA, succinic semialdehyde) and TCA cycle metabolites (citrate, malate, fumarate, isocitrate, lactate) were significantly low in the homozygous knock-out aldh7a1 zebrafish compared to the wildtype zebrafish. Homozygous knock-out aldh7a1 zebrafish had decreased electron transport chain enzyme activities compared to wildtype zebrafish. DISCUSSION: We report impaired electron transport chain function, accumulation of glutamate in the central nervous system and TCA cycle dysfunction in human PDE-ALDH7A1 and abnormal GABA pathway, TCA cycle and electron transport chain in knock-out aldh7a1 zebrafish. Central nervous system glutamate toxicity and impaired energy production may play important roles in the disease neuropathogenesis and severity in human PDE-ALDH7A1.

Sickle cell trait newborn screen results: disclosure and management.

This study aims to evaluate the notification process of sickle cell trait (SCT) identified by newborn screening in Alberta. On April 1, 2019, Alberta began newborn screening for sickle cell disease (SCD) and elected to report sickle cell trait (SCT). For 1 year, healthcare providers (HCPs) were sent a questionnaire which addressed the perceived importance of disclosing the SCT results, whether HCPs felt competent in disclosing the result, knowledge of available resources, and comfort with coordinating and interpreting testing for the newborn's parents. As a control, we collected data from HCPs receiving positive cystic fibrosis (CF) newborn screen results. A total of 107 out of 203 SCT questionnaires were returned and 41 of 66 CF questionnaires were returned. Respondents felt it was important that the results be shared with families (98% and 100%, respectively). Most respondents felt competent (SCT: 95%; CF: 85%), and willing to disclose the result to the family (SCT: 92%; CF: 88%). Fewer respondents were comfortable interpreting the results (SCT: 70%; CF: 51%)), and willing to arrange parental testing (SCT: 61%; CF: 59%). Family practitioners were significantly more willing to arrange SCT parental testing (88%) compared to pediatricians (40%) (OR = 5.3; CI 1.9, 15.4; p < 0.001). HCP comments revealed two themes: referral to another HCP for follow-up and identification of the primary HCP. Results support this disclosure process, and HCPs felt comfortable following up with SCT newborn screen results. The study identified challenges such as pediatricians being less comfortable ordering parental testing and the ordering HCP not always being the primary care provider.

Evaluating the relationship between health information technology and safer-prescribing in the long-term care setting: A systematic review.

BACKGROUND: The prevalence of health information technology (HIT) as an adjunct to increase safety and quality in healthcare applications is well known. There is a relationship between the use of HIT and safer-prescribing practices in long-term care. OBJECTIVE: The objective of this systematic review is to determine an association between the use of HIT and the improvement of prescription administration in long-term care facilities. METHODS: A systematic review was conducted using the MEDLINE and CINAHL databases. With the use of certain key terms, 66 articles were obtained. Each article was then reviewed by two researchers to determine if the study was germane to the research objective. If both reviewers agreed with using the article, it became a source for our review. The review was conducted and structured based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. RESULTS: The researchers identified 14 articles to include in a group for analysis from North America, Europe, and Australia. Electronic health records and electronic medication administration records were the two most common forms of technological interventions (6 of 14, 43%). Reduced risk, decreased error, decreased missed dosage, improved documentation, improved clinical process, and stronger clinical focus comprised 92% of the observations. CONCLUSIONS: HIT has shown beneficial effects for many healthcare organizations. Long-term care facilities that implemented health information technologies, have shown reductions in adverse drug events caused by medication errors overall reduced risk to the organization. The implementation of new technologies did not increase the time nurses spent on medication rounds.

Acute, Exercise-Induced Alterations in Cytokines and Chemokines in the Blood Distinguish Physically Active and Sedentary Aging.

Aging results in a chronic, proinflammatory state which can promote and exacerbate age-associated diseases. In contrast, physical activity in older adults improves whole body health, protects against disease, and reduces inflammation, but the elderly are less active making it difficult to disentangle the effects of aging from a sedentary lifestyle. To interrogate this interaction, we analyzed peripheral blood collected at rest and postexercise from 68 healthy younger and older donors that were either physically active aerobic exercisers or chronically sedentary. Subjects were profiled for 44 low-abundance cytokines, chemokines, and growth factors in peripheral blood. At rest, we found that regular physical activity had no impact on the age-related elevation in circulating IL-18, eotaxin, GRO, IL-8, IP-10, PDGF-AA, or RANTES. Similarly, there was no impact of physical activity on the age-related reduction in VEGF, EGF, or IL-12 (p70). However, older exercisers had lower resting plasma fractalkine, IL-3, IL-6, and TNF-α compared to sedentary older adults. In contrast to our resting characterization, blood responses following acute exercise produced more striking difference between groups. Physically active younger and older subjects increased over 50% of the analyzed factors in their blood which resulted in both unique and overlapping exercise signatures. However, sedentary individuals, particularly the elderly, had few detectable changes in response to exercise. Overall, we show that long-term physical activity has a limited effect on age-associated changes in basal cytokines and chemokines in the healthy elderly, yet physically active individuals exhibit a broader induction of factors postexercise irrespective of age.

Urine creatine metabolite panel as a screening test in neurodevelopmental disorders.

BACKGROUND: Cerebral creatine deficiency disorders (CCDD) are inherited metabolic disorders of creatine synthesis and transport. Urine creatine metabolite panel is helpful to identify these disorders. METHODS: We reviewed electronic patient charts for all patients that underwent urine creatine metabolite panel testing in the metabolic laboratory at our institution. RESULTS: There were 498 tests conducted on 413 patients. Clinical, molecular genetics and neuroimaging features were available in 318 patients. Two new patients were diagnosed with creatine transporter deficiency: one female and one male, both had markedly elevated urine creatine. Urine creatine metabolite panel was also used as a monitoring test in our metabolic laboratory. Diagnostic yield of urine creatine metabolite panel was 0.67% (2/297). There were six known patients with creatine transporter deficiency. The prevalence of creatine transporter deficiency was 2.64% in our study in patients with neurodevelopmental disorders who underwent screening or monitoring of CCDS at our institution. CONCLUSION: Even though the diagnostic yield of urine creatine metabolite panel is low, it can successfully detect CCDD patients, despite many neurodevelopmental disorders are not a result of CCDD. To the best of our knowledge, this study is the first Canadian study to report diagnostic yield of urine creatine metabolite panel for CCDD from a single center.

Homozygous GLUL deletion is embryonically viable and leads to glutamine synthetase deficiency.

Glutamine synthetase (GS) is the enzyme responsible for the biosynthesis of glutamine, providing the only source of endogenous glutamine necessary for several critical metabolic and developmental pathways. GS deficiency, caused by pathogenic variants in the glutamate-ammonia ligase (GLUL) gene, is a rare autosomal recessive inborn error of metabolism characterized by systemic glutamine deficiency, persistent moderate hyperammonemia, and clinically devastating seizures and multi-organ failure shortly after birth. The four cases reported thus far were caused by homozygous GLUL missense variants. We report a case of GS deficiency caused by homozygous GLUL gene deletion, diagnosed prenatally and likely representing the most severe end of the spectrum. We expand the known phenotype of this rare condition with novel dysmorphic, radiographic and neuropathologic features identified on post-mortem examination. The biallelic deletion identified in this case also included the RNASEL gene and was associated with immune dysfunction in the fetus. This case demonstrates that total absence of the GLUL gene in humans is viable beyond the embryonic period, despite the early embryonic lethality found in GLUL animal models.

Whole-exome sequencing identifies a homozygous pathogenic variant in TAT in a girl with palmoplantar keratoderma.

Palmoplantar keratoderma (PPK) is a defect in cornification that is characterized by progressive hyperkeratosis of palms and soles. Many phenotypes are linked with PPK, making exome-based diagnosis increasingly efficient. In this report, we identified tyrosinemia type II on whole-exome sequencing in a 7-year-old Syrian refugee that presented with PPK. Dietary therapy helped improve her overall symptoms.

Homozygous pathogenic variant in BRAT1 associated with nonprogressive cerebellar ataxia.

OBJECTIVE: To investigate the pathogenicity of a novel homozygous BRAT1 variant in 2 siblings with nonprogressive cerebellar ataxia (NPCA) through functional studies on primary and immortalized patient cell lines. METHODS: BRAT1 protein levels and ataxia-telangiectasia mutated (ATM) kinase activity in patient-derived and control cell lines were assessed by Western blotting. The impact of the novel BRAT1 variants on mitochondrial function was also assessed, by comparing patient and control cell lines for rates of oxygen consumption and for phosphorylation (S293) of the E1⍺ subunit of pyruvate dehydrogenase (PDH). RESULTS: Two male siblings with NPCA, mild intellectual disability, and isolated cerebellar atrophy were found to be homozygous for a c.185T>A (p.Val62Glu) variant in BRAT1 by whole exome sequencing. Western blotting revealed markedly decreased BRAT1 protein levels in lymphocytes and/or fibroblast cells from both affected siblings compared to control cell lines. There were no differences between the patient and control cells in ATM kinase activation, following ionizing radiation. Mitochondrial studies were initially suggestive of a defect in regulation of PDH activity, but there was no evidence of increased phosphorylation of the E1⍺ subunit of the PDH complex. Measurement of oxygen consumption rates similarly failed to identify differences between patient and control cells. CONCLUSIONS: Biallelic pathogenic variants in BRAT1 can be associated with NPCA, a phenotype considerably milder than previously reported. Surprisingly, despite the molecular role currently proposed for BRAT1 in ATM regulation, this disorder is unlikely to result from defective ATM kinase or mitochondrial dysfunction.

Expanding the Clinical Spectrum of LONP1-Related Mitochondrial Cytopathy.

Pathogenic variants in the LONP1 gene have been associated with CODAS syndrome (Cerebral, Ocular, Dental, Auricular, and Skeletal Anomalies Syndrome). A recent report identified the first newborn case with LONP1-related mitochondrial cytopathy due to a compound heterozygous pathogenic variant in LONP1 without features of CODAS. The proband had manifested with severe congenital lactic acidosis and profound multiple respiratory chain complex activity deficiencies associated with the quantitative loss of mtDNA copy number in muscle. A subsequent report identified two siblings with regression during infancy, profound hypotonia and muscle weakness, severe intellectual disability, progressive cerebellar atrophy, where muscle biopsy showed an electron dense mitochondrial inclusions without ragged-red fibers and normal electron transport chain enzyme activities. Here, we report an additional case of autosomal recessive mitochondrial cytopathy due to a homozygous missense variant in LONP1 that was identified on whole exome sequencing (c.810G > A; p.D463N). The proband, a 20-year-old male born to consanguineous parents, presented with global developmental delay, emotional outbursts, speech and swallowing difficulties, hypotonia, and ataxia since childhood. Muscle biopsy showed massive granular bodies, increased oxidative stress, and autophagic block and reduced mitochondrial state 3 respiration. We have identified another case of LONP1-related mitochondrial cytopathy further confirming a neurological phenotype without CODAS features.

Myasthenia graves-like symptoms associated with rare mitochondrial mutation (m.5728T>C).

We report here on a patient who presented with myasthenia gravis type symptoms (fatigable ptosis, increased jitter on single fiber EMG, and a thymic mass) who was subsequently diagnosed with a mitochondrial myopathy. Sequencing of the mitochondrial genome (mtDNA) identified a transition variant in the tRNA asparagine gene (MT-TN) (m.5728T>C) at in 41% of mtDNA molecules in muscle tissue. The variant was not detectable in blood. The m.5728T>C variant has been reported previously in a ten year old male with global developmental delays, failure to thrive, ataxia, weakness, cognitive regression, seizures, and glomerulosclerosis. The variant was seen in 97% of mtDNA molecules in muscle and 50% in blood. This case report supports the pathogenicity of the m.5728T>C and helps to establish the phenotypic spectrum of this condition at a lower heteroplasmy.

Severe cystic degeneration and intractable seizures in a newborn with molybdenum cofactor deficiency type B.

Newborns with cystic degeneration with or without intractable seizures should be investigated for inborn errors of metabolism, including molybdenum cofactor deficiency (MoCoD). MoCoD may present with non-specific hypoxic ischemic injury in the neonatal period with MRI showing extensive prenatally acquired cystic encephalomalacia involving grey and white matter. Most newborns with MoCoD will present with normal head size and brain appearance at birth and postnatally rapidly develop cystic encephalomalacia. A significant minority will present with signs of prenatal brain injury or malformation. It is important to consider the diagnosis in both scenarios. Low plasma urate and homocysteine may help direct the diagnostic evaluation. Herein, we describe the clinical, radiological and biochemical features of a newborn with MoCoD that was initially suspected of having the condition on biochemical screening and confirmed on rapid whole exome sequencing.

Exercise-stimulated interleukin-15 is controlled by AMPK and regulates skin metabolism and aging.

Aging is commonly associated with a structural deterioration of skin that compromises its barrier function, healing, and susceptibility to disease. Several lines of evidence show that these changes are driven largely by impaired tissue mitochondrial metabolism. While exercise is associated with numerous health benefits, there is no evidence that it affects skin tissue or that endocrine muscle-to-skin signaling occurs. We demonstrate that endurance exercise attenuates age-associated changes to skin in humans and mice and identify exercise-induced IL-15 as a novel regulator of mitochondrial function in aging skin. We show that exercise controls IL-15 expression in part through skeletal muscle AMP-activated protein kinase (AMPK), a central regulator of metabolism, and that the elimination of muscle AMPK causes a deterioration of skin structure. Finally, we establish that daily IL-15 therapy mimics some of the anti-aging effects of exercise on muscle and skin in mice. Thus, we elucidate a mechanism by which exercise confers health benefits to skin and suggest that low-dose IL-15 therapy may prove to be a beneficial strategy to attenuate skin aging.

Daily chocolate milk consumption does not enhance the effect of resistance training in young and old men: a randomized controlled trial.

Older and younger men completed 12 weeks of resistance training and ingested either 500 mL of chocolate milk or placebo daily. Training increased strength in both age groups (p < 0.05), with no supplementation effect. Type I muscle fibre area increased with training (p = 0.008) with no effect of age or supplementation. Type II fibre area increased (p = 0.014) in young men only with no supplementation effect. Chocolate milk did not enhance skeletal muscle hypertrophy following training.

The order of exercise during concurrent training for rehabilitation does not alter acute genetic expression, mitochondrial enzyme activity or improvements in muscle function.

Concurrent exercise combines different modes of exercise (e.g., aerobic and resistance) into one training protocol, providing stimuli meant to increase muscle strength, aerobic capacity and mass. As disuse is associated with decrements in strength, aerobic capacity and muscle size concurrent training is an attractive modality for rehabilitation. However, interference between the signaling pathways may result in preferential improvements for one of the exercise modes. We recruited 18 young adults (10 ♂, 8 ♀) to determine if order of exercise mode during concurrent training would differentially affect gene expression, protein content and measures of strength and aerobic capacity after 2 weeks of knee-brace induced disuse. Concurrent exercise sessions were performed 3x/week for 6 weeks at gradually increasing intensities either with endurance exercise preceding (END>RES) or following (RES>END) resistance exercise. Biopsies were collected from the vastus lateralis before, 3 h after the first exercise bout and 48 h after the end of training. Concurrent exercise altered the expression of genes involved in mitochondrial biogenesis (PGC-1α, PRC, PPARγ), hypertrophy (PGC-1α4, REDD2, Rheb) and atrophy (MuRF-1, Runx1), increased electron transport chain complex protein content, citrate synthase and mitochondrial cytochrome c oxidase enzyme activity, muscle mass, maximum isometric strength and VO 2peak. However, the order in which exercise was completed (END>RES or RES>END) only affected the protein content of mitochondrial complex II subunit. In conclusion, concurrent exercise training is an effective modality for the rehabilitation of the loss of skeletal muscle mass, maximum strength, and peak aerobic capacity resulting from disuse, regardless of the order in which the modes of exercise are performed.

Defects in mitochondrial DNA replication and oxidative damage in muscle of mtDNA mutator mice.

A causal role for mitochondrial dysfunction in mammalian aging is supported by recent studies of the mtDNA mutator mouse ("PolG" mouse), which harbors a defect in the proofreading-exonuclease activity of mitochondrial DNA polymerase gamma. These mice exhibit accelerated aging phenotypes characteristic of human aging, including systemic mitochondrial dysfunction, exercise intolerance, alopecia and graying of hair, curvature of the spine, and premature mortality. While mitochondrial dysfunction has been shown to cause increased oxidative stress in many systems, several groups have suggested that PolG mutator mice show no markers of oxidative damage. These mice have been presented as proof that mitochondrial dysfunction is sufficient to accelerate aging without oxidative stress. In this study, by normalizing to mitochondrial content in enriched fractions we detected increased oxidative modification of protein and DNA in PolG skeletal muscle mitochondria. We separately developed novel methods that allow simultaneous direct measurement of mtDNA replication defects and oxidative damage. Using this approach, we find evidence that suggests PolG muscle mtDNA is indeed oxidatively damaged. We also observed a significant decrease in antioxidants and expression of mitochondrial biogenesis pathway components and DNA repair enzymes in these mice, indicating an association of maladaptive gene expression with the phenotypes observed in PolG mice. Together, these findings demonstrate the presence of oxidative damage associated with the premature aging-like phenotypes induced by mitochondrial dysfunction.

Redox state and mitochondrial respiratory chain function in skeletal muscle of LGMD2A patients.

BACKGROUND: Calpain-3 deficiency causes oxidative and nitrosative stress-induced damage in skeletal muscle of LGMD2A patients, but mitochondrial respiratory chain function and anti-oxidant levels have not been systematically assessed in this clinical population previously. METHODS: We identified 14 patients with phenotypes consistent with LGMD2A and performed CAPN3 gene sequencing, CAPN3 expression/autolysis measurements, and in silico predictions of pathogenicity. Oxidative damage, anti-oxidant capacity, and mitochondrial enzyme activities were determined in a subset of muscle biopsies. RESULTS: Twenty-one disease-causing variants were detected along the entire CAPN3 gene, five of which were novel (c.338 T>C, c.500 T>C, c.1525-1 G>T, c.2115+4 T>G, c.2366 T>A). Protein- and mRNA-based tests confirmed in silico predictions and the clinical diagnosis in 75% of patients. Reductions in antioxidant defense mechanisms (SOD-1 and NRF-2, but not SOD-2), coupled with increased lipid peroxidation and protein ubiquitination, were observed in calpain-3 deficient muscle, indicating a redox imbalance primarily affecting non-mitochondrial compartments. Although ATP synthase levels were significantly lower in LGMD2A patients, citrate synthase, cytochrome c oxidase, and complex I+III activities were not different from controls. CONCLUSIONS: Despite significant oxidative damage and redox imbalance in cytosolic/myofibrillar compartments, mitochondrial respiratory chain function is largely maintained in skeletal muscle of LGMD2A patients.

Impact of habitual exercise on the strength of individuals with myotonic dystrophy type 1.

OBJECTIVE: It remains unclear whether habitual physical activity can attenuate the rate of progressive muscle strength loss in individuals with myotonic dystrophy type 1 (DM1). The aim of this study was to identify whether there were any strength differences between DM1 patients who were habitually active or sedentary. DESIGN: Knee extension, handgrip, and elbow flexion quantitative strength measurements were investigated in the DM1 patients using isokinetic dynamometry. Strength was compared between the patients who followed self-selected formal exercise plans for at least 1 yr, those who were sedentary (controls), and those who initiated or terminated a formal exercise routine. RESULTS: Physically active DM1 patients with midrange CTG repeat size (100-500 CTG repeat sizes) had significantly stronger handgrip and knee extension and elbow flexion torques as compared with their sedentary counterparts with the same CTG repeat range. The DM1 patients who began a formal exercise routine experienced a significant improvement in knee extension torque measurements (+24.3%) in comparison with those who were habitually active or sedentary. CONCLUSIONS: These data suggest that there is an association between physical activity and strength. This may be shown to be a useful tool for the management of this condition. Further investigations into the relationships between physical exercise, muscle weakness, and genetic factors are needed before evidence-based recommendations can be made.

Functional impairment in patients with sporadic Inclusion Body Myositis.

INTRODUCTION: We conducted a retrospective chart review of 53 patients diagnosed with sporadic Inclusion Body Myositis (sIBM) who have been followed at the McMaster Neuromuscular Clinic since 1996. OBJECTIVES: We reviewed patient medical histories in order to compare our findings with similar cohorts, and analyzed quantitative strength data to determine functionality in guiding decisions related to gait assistive devices. METHODS: Patient information was acquired through retrospective clinic chart review. RESULTS: Our study found knee extension strength decreased significantly as patients transitioned to using more supportive gait assistive devices (P < 0.05). A decline to below 30 Nm was particularly indicative of the need for a preliminary device (i.e. cane)(P < 0.05). Falls and fear of falling poses a significant threat to patient physical well-being. The prevalence of dysphagia increased as patients required more supportive gait devices, and finally a significant negative correlation was found between time after onset and creatine kinase (CK) levels (P < 0.01). CONCLUSION: This study supports that knee extension strength may be a useful tool in advising patients concerning ambulatory assistance. Further investigations concerning gait assistive device use and patient history of falling would be beneficial in preventing future falls and improving long-term patient outcomes.

Genome-wide DNA methylation changes with age in disease-free human skeletal muscle.

A decline in skeletal muscle mass and function with aging is well recognized, but remains poorly characterized at the molecular level. Here, we report for the first time a genome-wide study of DNA methylation dynamics in skeletal muscle of healthy male individuals during normal human aging. We predominantly observed hypermethylation throughout the genome within the aged group as compared to the young subjects. Differentially methylated CpG (dmCpG) nucleotides tend to arise intragenically and are underrepresented in promoters and are overrepresented in the middle and 3' end of genes. The intragenic methylation changes are overrepresented in genes that guide the formation of the junction of the motor neuron and myofibers. We report a low level of correlation of gene expression from previous studies of aged muscle with our current analysis of DNA methylation status. For those genes that had both changes in methylation and gene expression with age, we observed a reverse correlation, with the exception of intragenic hypermethylated genes that were correlated with an increased gene expression. We suggest that a minimal number of dmCpG sites or select sites are required to be altered in order to correlate with gene expression changes. Finally, we identified 500 dmCpG sites that perform well in discriminating young from old samples. Our findings highlight epigenetic links between aging postmitotic skeletal muscle and DNA methylation.